Describe the extent and nature of
diseases
Provide more comprehensive and
accurate information for basic
researches
Serve as starting point for etiological
studies
Needed for monitoring and evaluation
of disease control activity.

Incidence
The number of new cases occurring in a
define population during specific period
of time
ď Ž Incidence rate =
No of new cases of specific D
during specific period of time X 1000
Population at risk during that period
ď Ž

Incidence
Incidence refers :
 Only new cases
 During a given time
 Specific population ( at risk)
 New spell or episodes of disease